This is a note to let you know that I've just added the patch titled
drm: buddy_allocator: Fix buddy allocator init on 32-bit systems
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-buddy_allocator-fix-buddy-allocator-init-on-32-b.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4d9fe640610f3aefff4f212b9bd3ebe0b2e692a0
Author: David Gow <davidgow@xxxxxxxxxx>
Date: Wed Mar 29 14:55:32 2023 +0800
drm: buddy_allocator: Fix buddy allocator init on 32-bit systems
[ Upstream commit 4453545b5b4c3eff941f69a5530f916d899db025 ]
The drm buddy allocator tests were broken on 32-bit systems, as
rounddown_pow_of_two() takes a long, and the buddy allocator handles
64-bit sizes even on 32-bit systems.
This can be reproduced with the drm_buddy_allocator KUnit tests on i386:
./tools/testing/kunit/kunit.py run --arch i386 \
--kunitconfig ./drivers/gpu/drm/tests drm_buddy
(It results in kernel BUG_ON() when too many blocks are created, due to
the block size being too small.)
This was independently uncovered (and fixed) by Luís Mendes, whose patch
added a new u64 variant of rounddown_pow_of_two(). This version instead
recalculates the size based on the order.
Reported-by: Luís Mendes <luis.p.mendes@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/CAEzXK1oghXAB_KpKpm=-CviDQbNaH0qfgYTSSjZgvvyj4U78AA@xxxxxxxxxxxxxx/T/
Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
Acked-by: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Arunpravin Paneer Selvam <arunpravin.paneerselvam@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20230329065532.2122295-1-davidgow@xxxxxxxxxx
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 3d1f50f481cfd..7098f125b54a9 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -146,8 +146,8 @@ int drm_buddy_init(struct drm_buddy *mm, u64 size, u64 chunk_size)
unsigned int order;
u64 root_size;
- root_size = rounddown_pow_of_two(size);
- order = ilog2(root_size) - ilog2(chunk_size);
+ order = ilog2(size) - ilog2(chunk_size);
+ root_size = chunk_size << order;
root = drm_block_alloc(mm, NULL, order, offset);
if (!root)
